Laser shutting device and laser scanning unit employing the same

Abstract

A laser shutting device blocks laser beams in a laser scanning unit that includes a light source that emits laser beams and a beam deflecting unit that deflects the laser beams in a main-scanning direction and is adapted to form an image on a photosensitive body using the laser beams. The laser shutting device includes a shutter movably installed in a light path between the light source and the photosensitive body, an opening formed in the shutter that allows the laser beams to pass therethrough, and a laser shutting unit that moves the shutter using an electromagnet according to a start signal for operating the beam reflecting unit so that the laser beams can pass through the opening.

1. A laser shutting device for blocking laser beams in a laser scanning unit that includes a light source that emits laser beams and a beam deflecting unit that deflects the laser beams in a main-scanning direction, and is adapted to form an image on a photosensitive body using the laser beams, the laser shutting device comprising:
 a shutter movably installed in a light path between the light source and the photosensitive body; 
 an opening formed in the shutter that allows the laser beams to pass therethrough; and 
 a laser shutting unit that moves the shutter according to a start signal for operating the beam reflecting unit so that the laser beams can pass through the opening. 
 
   
   
     2. The laser shutting device of  claim 1 , wherein the laser shutting unit comprises:
 a ferromagnetic plate attached to one side of the shutter; 
 an electromagnet that attracts the ferromagnetic plate when receiving the start signal; and 
 an elastic member coupled between the ferromagnetic plate and the electromagnet. 
 
   
   
     3. The laser shutting device of  claim 2 , wherein the laser shutting unit further comprises:
 an electromagnet driving unit that receives the start signal and supplies power to the electromagnet. 
 
   
   
     4. The laser shutting device of  claim 2 , wherein
 the electromagnet driving unit cuts off the power supply to the electromagnet when the operation of the beam deflecting unit stops. 
 
   
   
     5. The laser shutting device of  claim 2 , wherein
 the elastic member is a spring member. 
 
   
   
     6. The laser shutting device of  claim 2 , wherein
 the shutter is movable substantially perpendicular to the light path between the light source and the beam deflecting unit. 
 
   
   
     7. The laser shutting device of  claim 2 , wherein
 the electromagnet comprises a cylindrical core and a coil wound around the core, and an end portion of the shutter is inserted to a predetermined depth into the core. 
 
   
   
     8. A laser scanning unit comprising:
 a light source that emits laser beams; 
 a beam deflecting unit that deflects the laser beams in a main-scanning direction; 
 a photosensitive body on which the deflected laser beams form an image; and 
 a laser shutting device that prevents the laser beams from leaking out, the laser shutting device comprising: 
 a shutter movably installed in a light path between the light source and the photosensitive body; 
 an opening formed in the shutter that allows the laser beams to pass therethrough; and 
 a laser shutting unit that moves the shutter according to a start signal for operating the beam deflecting unit so that the laser beams can pass through the opening. 
 
   
   
     9. The laser scanning unit of  claim 8 , wherein the laser shutting unit comprises:
 a ferromagnetic plate attached to one side of the shutter; 
 an electromagnet that attracts the ferromagnetic plate when receiving the start signal; and 
 an elastic member coupled between the ferromagnetic plate and the electromagnet. 
 
   
   
     10. The laser scanning unit of  claim 9 , wherein the laser shutting unit further comprises:
 an electromagnet driving unit that receives the start signal and supplies power to the electromagnet. 
 
   
   
     11. The laser scanning unit of  claim 9 , wherein
 the electromagnet driving unit cuts off the power supply to the electromagnet when the operation of the beam deflecting unit stops. 
 
   
   
     12. The laser scanning unit of  claim 9 , wherein
 the elastic member is a spring member. 
 
   
   
     13. The laser scanning unit of  claim 9 , further comprising:
 guides installed on both surfaces of the shutter to prevent the shutter from being shaken. 
 
   
   
     14. The laser scanning unit of  claim 8 , further comprising:
 a collimating lens located in the light path between the light source and the photosensitive body; and 
 a cylindrical lens located in the light path between the light source and the photosensitive body. 
 
   
   
     15. The laser scanning unit of  claim 14 , wherein
 the laser shutting device is located between the cylindrical lens and beam deflecting unit. 
 
   
   
     16. A laser scanning unit comprising:
 a light source that emits laser beams; 
 a rotating polygonal mirror driven by a motor that deflects the laser beams generated by the light source; and 
 a laser shutting device that blocks the laser beams, the laser shutting device comprising: 
 a shutter movably installed in the path of the laser beams emitted by the light source, the shutter having an opening to allow the laser beams to pass through the shutter; and 
 a laser shutting unit that moves the shutter between an open position where the laser beams can pass through the opening and a closed position where the shutter blocks the path of the laser beams, the laser shutting unit moving the shutter to the open position in accordance with a start to operate the motor for the polygonal mirror. 
 
   
   
     17. The laser scanning unit according to  claim 16 , wherein
 the laser shutting unit includes an electromagnetic coil for moving the shutter. 
 
   
   
     18. The laser scanning unit according to  claim 17 , further comprising
 an electromagnet driving unit that receives the start signal motor for the polygonal mirror and supplies power to the electromagnet.